<?php
/**
 * Created by PhpStorm.
 * User: yangwenqu
 * Date: 2018/4/20
 * Time: 15:52
 */

/**
 * @param $a
 * @param $b
 * @return mixed
 */
function add($a, $b)
{
    return $a + $b;
}

function merge($a, $b, $c)
{
    return array_merge($a, $b, $c);
}

call_user_func(function ($string) {
    echo $string . PHP_EOL;
}, "Hello World");

$sum = call_user_func('add', 1, 2);
print $sum;

print_r(call_user_func('merge', [1, 2], [3, 4], [5, 6]));